Consolidate Dockerfiles, improve compose UX, and add documentation

[AndrewGearhart]

Note: This PR depends on the changes in PR #1: import-hax-docker. Please review and merge that PR first. After merging, rebase this branch onto main to ensure a clean history.

This PR addresses the following issues and improvements:

• Deprecates Dockerfile.devenv and Consolidates Dockerfile logic into a single multi-stage build
  (fixes #3)
• Switches to ubuntu:22.04-slim for reproducibility and smaller image size
  (fixes #4)
• Adds ubuntu user creation and fixes permissions
  (fixes #2)
• Cleans up package manager caches in build steps
  (fixes #5)
• Adds a .dockerignore file to exclude unnecessary, OS, and editor files
  (fixes #11)
• Fixes docker-compose port conflicts by assigning unique host ports
  (fixes #6)
• Renames services to simplehost and devenv, with comments for clarity; Adds container_name to each service for easier management
  (fixes #7)
• Adds named volumes for persistent data to both services
  (fixes #8)
• Expands README with usage instructions, prerequisites, and example commands
  (fixes #9)

How to proceed:

1. Review and merge the base PR (import-hax-docker) first.
2. Once the base PR is merged, this PR will automatically update to show only its unique changes.
3. Review and merge this PR.

This PR streamlines the developer and user experience, reduces duplication, and improves documentation and maintainability.

[winstonwumbo]

Thanks for your work on streamlining the proof-of-concept!